Propionaldehyde, reaction product with formaldehyde

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 December 2009 to 1 September 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Version / remarks:

2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

1984

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Preparation of inoculum for exposure: A sample of activated sludge was collected on the day before the test. The container for transportation was only maximally 2/3 filled in order to maintain the contact with air. At arrival in the laboratory (less than 1 hour after sample collection), the supernatantover the sludge was decanted, the sludge was diluted with tap water and aerated by means of compressed air. 50 mL of synthetic sewage concentrate were added per litre each day. On the day of the test the sludge was allowed to sediment and the supernatant was decanted.
- Initial biomass concentration: On the basis of this calculation the concentration of suspended solids was adjusted to 4 g/L
with tap water. 200 mL of this adjusted inoculum are added per test vessel, resulting in 1.6 g dry weight per litre in the samples.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

19°C

pH:

The pH of the incubation mixtures after the 3 hour incubation was between 8.12 and 8.27, the pH of the negative control samples was 8.26 and 8.31. The test substance did not influence the pH.The pH of the standardised activated sludge was 7.76.

Dissolved oxygen:

The oxygen concentration was determined with a DO-meter "OXI Level 2" and an oxygen electrode (Wissenschaftlich-technische Werkstätten G.m.b.H., Dr. rer.nat. K. Slevogt, D-82362 Weilheim i. OB, Trifthofstr. 57a). The readout was set to 100 % in water-saturated air.

Nominal and measured concentrations:

final conentrations*: 7.7 mg/l, 19.3 mg/l, 48.2 mg/l, 120.5 mg/l and 301.2 mg/L
*) The amount of test substance stated refers to the dry weight (the test substance contains 6 % water)

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beakers with a nominal volume of 1000 mL
- Type (delete if not applicable): open during 3h incubation.
- Material, size, headspace, fill volume: All incubation mixtures were prepared by adding 200 mL of microbial inoculum and 200 mL
of synthetic sewage solution to 100 mL of tap water and/or the appropriate amount of the test or control substance in glass beakers with a nominal volume of 1000 mL.
- Aeration: oil free compressed air, flow rate 0.7 L/min
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: local tap water was used.

OTHER TEST CONDITIONS
- Adjustment of pH: None.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.5

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (nominal concentrations: 5.0, 12.1 and 29.8 mg/L)

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

> 300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

> 300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

After 3 hours the EC50 was determined to be > 300 mg/L and the NOEC was determined to be 300 mg/L.

Results with reference substance (positive control):

The actual values of the EC20, EC50 and EC80 for 3,5-dichlorophenol were:
EC20 = 8.1 mg/L EC50 = 17.5 mg/L EC80 = 37.8 mg/L
- Results with reference substance valid? yes

Respiration rate and inhibition of samples

sample	final concentr. (mg/L)^*)	linear range (minutes)	mg O2/ L at begin	mg O2/ L at end	respiration rate (mg O2. L^-1. h^-1)	percent respiration inhibition
neg. control 1	0.0	7.40	5.48	2.15	27.00	0.11
test substance 1	7.7	7.36	6.23	3.06	25.84	4.40
test substance 2	19.3	7.84	5.89	2.24	27.93	-3.34
test substance 3	48.2	7.28	5.87	2.59	27.03	-0.01
test substance 4	120.5	7.52	6.08	2.66	27.29	-0.95
test substance 5	301.2	7.28	5.21	1.54	30.25	-11.90
neg. control 2	0.0	7.76	6.18	2.68	27.06	-0.11
DCP 1	5.0	8.12	5.79	2.08	27.41	-1.42
DCP 2	12.1	7.04	7.00	5.11	16.11	40.41
DCP 3	29.8	8.12	7.86	6.70	8.57	68.29

Validity criteria fulfilled:

yes

Conclusions:

A study on toxicity to microorganisms was performed according to the OECD 209. After 3 hours the EC50 was determined to be > 300 mg/L and the NOEC was determined to be 300 mg/L.

Executive summary:

The study was performed to estimate possible effects of the test substance on aerobic microbial sewage treatment plants. The test was performed according to the OECD Guideline for Testing of Chemicals 209 "Activated Sludge, Respiration Inhibition Test" and the EU-COUNCIL REGULATION (EC) No 440/2008, using activated sludge from a sewage treatment plant treating predominantly domestic sewage.

Five concentrations of the test substance (7.7, 19.3, 48.2, 120.5 and 301.2 mg/L) were tested versus two negative controls (tap water).

As positive control substance 3,5-dichlorophenol was used and tested in three concentrations (5.0, 12.1 and 29.8 mg/L).

The microbial inoculum was a preparation of activated sludge collected on the day before the test. 50 mL of synthetic sewage concentrate were addedper litre and the sludge was kept areated. On the day of the experiment, the concentration of the microbial inoculum was adjusted to 4 g of dry weightper litre which results in a final concentration of 1.6 g dry weight per litre in the samples.

After mixing the inoculum with synthetic sewage solution and appropriate dilutions of control or test substance solutions the samples were aerated for a contact time of 3 hours at 19 °C.

Negative controls were run before the first and after the last test substance sample. After incubation the respiration rates were determined in closed bottles using an oxygen sensitive electrode. The inhibition of respiration was calculated from the respiration rates using the mean value of the negative controls as 100 %.

The test results fulfilled the criteria for validity: the respiration rates of the two negative control samples were within 15 % of each other (actual values: + 0.1 %), the EC50 of 3,5 -dichlorophenol wasin the accepted range of 5 to 30 mg/L (actual EC50: 17.5 mg/L), the pH ofthe incubation mixtures with the test substance after the 3 hour incubation was between 8.12 and 8.27, the pH of the negative control samples was 8.26 and 8.31.

The test substance did notinhibit the respiration of the activated sludge. The respiration rates of all samples with the test substance were in the range of 95.6 to 111.9 % of the control value.

After 3 hours, the NOEC of the test substance was determined to be 300 mg/L and the EC50 was determined to be greater than 300 mg/L.

Description of key information

A study on toxicity to microorganisms was performed according to the OECD 209. After 3 hours the EC50 was determined to be > 300 mg/L and the NOEC was determined to be 300 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

300 mg/L

Additional information

The study was performed to estimate possible effects of the test substance on aerobic microbial sewage treatment plants. The test was performed according to the OECD Guideline for Testing of Chemicals 209 "Activated Sludge, Respiration Inhibition Test" and the EU-COUNCIL REGULATION (EC) No 440/2008, using activated sludge from a sewage treatment plant treating predominantly domestic sewage.

Five concentrations of the test substance(7.7, 19.3, 48.2, 120.5 and 301.2 mg/L) were tested versus two negative controls (tap water).

Aspositive control substance 3,5-dichlorophenol was used and tested in three concentrations (5.0, 12.1 and 29.8 mg/L).

The microbial inoculum was a preparation of activated sludge collected on the day before the test. 50 mL of synthetic sewage concentrate were addedper litre and the sludge was kept areated. On the day of the experiment, the concentration of the microbial inoculum was adjusted to 4 g of dry weightper litre which results in a final concentration of 1.6 g dry weight per litre in the samples.

After mixing the inoculum with synthetic sewage solution and appropriate dilutions of control or test substance solutions the samples were aerated for a contact time of 3 hours at 19 °C.

Negative controls were run before the first and after the last test substance sample. After incubation the respiration rates were determined in closed bottles using an oxygen sensitive electrode. The inhibition of respiration was calculated from the respiration rates using the mean value of the negative controls as 100 %.

The test results fulfilled the criteria for validity: the respiration rates of the two negative control samples were within 15 % of each other (actual values: + 0.1 %), the EC50 of 3,5 -dichlorophenol wasin the accepted range of 5 to 30 mg/L (actual EC50: 17.5 mg/L), the pH ofthe incubation mixtures with the test substance after the 3 hour incubation was between 8.12 and 8.27, the pH of the negative control samples was 8.26 and 8.31.

The test substance did notinhibit the respiration of the activated sludge. The respiration rates of all samples with the test substance were in the range of 95.6 to 111.9 % of the control value.

After 3 hours, the NOEC of the test substance was determined to be 300 mg/L and the EC50 was determined to be greater than 300 mg/L.